If it is eventually possible to make available to the clinician from surface recordings, information from the Bundle of His and the bundle branches, the whole sphere of electrocardiography as a fundamental screening and diagnostic tool will be greatly expanded. At present it is necessary to employ invasive cardiac catheterization in order to gather this data, with its attendant discomfort and risks as well as its significant economic burden. If these data can be obtained at the same recording session as the clinical electrocardiogram, not only will society be benefited from the health standpoint and economic standpoint, but the field of research into problems in cardiac conduction and arrhythmias, antiarrhythmic drug testing, and studies of the mechanism of the genesis of arrhythmias will be greatly enhanced. The overall objective is to demonstrate that a practical recording system is possible so that information from the Bundle of His and the bundle branches ultimately may become a part of routine electrocardiography just as the P. QRS, and T are at present.